/**
 * Copyright (C) 2002-2015   The FreeCol Team
 * <p>
 * This file is part of FreeCol.
 * <p>
 * FreeCol is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 * <p>
 * FreeCol is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 * <p>
 * You should have received a copy of the GNU General Public License
 * along with FreeCol.  If not, see <http://www.gnu.org/licenses/>.
 */

package net.sf.freecol.common.model;

import javax.xml.stream.XMLStreamException;

import net.sf.freecol.common.i18n.Messages;
import net.sf.freecol.common.io.FreeColXMLReader;
import net.sf.freecol.common.io.FreeColXMLWriter;
import net.sf.freecol.common.util.Utils;


/**
 * A trade item consisting of a unit.
 */
public class UnitTradeItem extends TradeItem
{

    /** The unit to change hands. */
    private Unit unit;


    /**
     * Creates a new <code>UnitTradeItem</code> instance.
     *
     * @param game The enclosing <code>Game</code>.
     * @param source The source <code>Player</code>.
     * @param destination The destination <code>Player</code>.
     * @param unit The <code>Unit</code> to trade.
     */
    public UnitTradeItem( Game game, Player source, Player destination,
                          Unit unit )
    {
        super( game, Messages.nameKey( "model.tradeItem.unit" ),
               source, destination );

        this.unit = unit;
    }

    /**
     * Creates a new <code>UnitTradeItem</code> instance.
     *
     * @param game The enclosing <code>Game</code>.
     * @param xr The <code>FreeColXMLReader</code> to read from.
     * @exception XMLStreamException if there is a problem reading the stream.
     */
    public UnitTradeItem( Game game, FreeColXMLReader xr ) throws XMLStreamException
    {
        super( game, xr );
    }


    // Interface TradeItem

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isValid( )
    {
        return unit.getOwner( ) == getSource( )
                && unit.getType( ).isAvailableTo( getDestination( ) );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean isUnique( )
    {
        return false;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public StringTemplate getLabel( )
    {
        return unit.getLabel( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public Unit getUnit( )
    {
        return unit;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void setUnit( Unit unit )
    {
        this.unit = unit;
    }

    /**
     * {@inheritDoc}
     */
    public int evaluateFor( Player player )
    {
        final Unit unit = getUnit( );
        return ( ! isValid( ) ) ? Integer.MIN_VALUE
                : ( getSource( ) == player )
                ? - unit.evaluateFor( player )
                : unit.evaluateFor( player );
    }


    // Override Object

    /**
     * {@inheritDoc}
     */
    @Override
    public boolean equals( Object other )
    {
        if ( other instanceof UnitTradeItem )
        {
            return Utils.equals( this.unit, ( ( UnitTradeItem ) other ).unit )
                    && super.equals( other );
        }
        return false;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public int hashCode( )
    {
        int hash = super.hashCode( );
        return 37 * hash + Utils.hashCode( this.unit );
    }


    // Serialization

    private static final String UNIT_TAG = "unit";


    /**
     * {@inheritDoc}
     */
    @Override
    protected void writeAttributes( FreeColXMLWriter xw ) throws XMLStreamException
    {
        super.writeAttributes( xw );

        xw.writeAttribute( UNIT_TAG, unit );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String toString( )
    {
        StringBuilder sb = new StringBuilder( 16 );
        sb.append( "[" ).append( getId( ) )
                .append( " " ).append( unit.getId( ) ).append( "]" );
        return sb.toString( );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    protected void readAttributes( FreeColXMLReader xr ) throws XMLStreamException
    {
        super.readAttributes( xr );

        unit = xr.getAttribute( getGame( ), UNIT_TAG, Unit.class, ( Unit ) null );
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public String getXMLTagName( ) { return getXMLElementTagName( ); }

    /**
     * Gets the tag name of the root element representing this object.
     *
     * @return "unitTradeItem".
     */
    public static String getXMLElementTagName( )
    {
        return "unitTradeItem";
    }
}
